backstage/.changeset/rich-ducks-ring.md

@backstage/catalog-client, @backstage/plugin-catalog-backend

@backstage/catalog-client	@backstage/plugin-catalog-backend
minor	minor

Added predicate-based entity filtering via POST /entities/by-query endpoint.

Supports $all, $any, $not, $exists, $in, $hasPrefix, and (partially) $contains operators for expressive entity queries. Integrated into the existing queryEntities flow with full cursor-based pagination, permission enforcement, and totalItems support.

The catalog client's queryEntities() method automatically routes to the POST endpoint when a query predicate is provided.